May 2 marks the day of a very important anniversary to nearly everyone in the United States and around the globe. No, I’m not referring to the death of Osama Bin Laden or the birth of this generation’s greatest actor, Dwayne “The Rock” Johnson. What I’m talking about happened way back in the year 2000 when “Selective Availability” was discontinued. You may be asking, what is Selective Availability? Well, prior to 2000, it maintained that civilian users of GPS (Global Positioning System for those of you who hate acronyms) would receive a degraded signal which severely limited accuracy. When it comes to engineering and surveying, accuracy is key.
Nowadays, GPS is used in everything from phones, planes, trains and automobiles to drones, survey equipment and even shopping carts. But like most technology we know today, it started in the military. During the 1960s, in the depths of the Cold War, the Air Force, Navy and Army were all developing their own technologies to improve navigation, missile guidance, etc. In 1973, everyone put their heads together, and the U.S. Department of Defense started the GPS project. Once 1978 came around, the first GPS satellite was launched. Subsequent years saw the launching of more satellites under the watchful eye of the military.
The movement to make GPS freely available can be narrowed down to one horrific event. On September 1, 1983, 269 people were killed when Korean Air Lines Flight 007 was shot down by a Soviet aircraft after entering prohibited airspace in Northeast Asia because of navigational errors. President Ronald Reagan issued a directive making GPS freely available for civilian use. The caveat was that it had to be sufficiently developed and had to be used as a common good.
From that moment forward, the military would continue to upgrade the technology associated with GPS, all the while Selective Availability intentionally degraded the signal for everyone else. Accuracy could vary wildly depending on where you were and where the satellites were currently positioned. Initially the average civilian GPS receiver was accurate to about 100 meters. In 1996, Bill Clinton issued a policy directive declaring GPS a dual-use system to be used for both the military and the general population. On May 2, 2000, Selective Availability was discontinued, and people could now get an accurate signal in their equipment. GPS systems have since continued to evolve and have become a technology that almost everyone uses daily. Many receivers are accurate down to the foot, even down to the millimeter if you’re using Howell Surveying equipment. So, when you check your phone today or drive your car home, take a moment to think about how far technology has come, knowing there’s a GPS receiver tracking every move you make.
Also, Happy Birthday, Dwayne Johnson!
